1. Field of the Invention
The invention relates to a spin-stabilized projectile which contains a releasable payload. Within the scope of the invention, the term "payload" may be understood as a quantity of transport material contained in a payload chamber.
Projectiles of this type may transport various payloads for various purposes, e.g., military purposes or civil purposes. Meteorology is one example of a civil purposes. These projectiles may also be implemented for various uses, i.e. surface to surface, surface to air, air to surface, and air to air.
Given equal overall volume and weight, a projectile becomes more efficient as payload increases. Therefore, it is desirable to take as much advantage of the available space in the payload chamber, i.e. housing the payload as densely as possible in the payload chamber. The optimum utilization of available space may be achieved when the payload completely fills the payload chamber, i.e., the cross section of the payload is equal to the cross-section of the payload chamber. The payload may be divided into columns, in which case the best use of space may be achieved when the columns are configured to spatially fill as large an area as possible with the payload.
This could be achieved with columns including cross sections of, for example, rectangular, square, triangular, or regularly hexagonal shape. However, in addition to the cross-section of the column, other demands may need to be met, for example, cost, ease of manufacture and assembly, control of flight by spin-stabilization, etc. In general, columns with round cross-sections may be used, and may include projections for an arrow stabilization. Round cross-sections are superior to the other above-mentioned designs, except with respect to maximizing use of space or packing density.
2. Discussion of the Background of the Invention
Conventionally, the payload is released as the outer shell is exploded by the ignition of an explosive charge and/or the sub-projectiles were ejected from the outer shell by the ignition of an ejection charge. A considerable quantity of explosive was required for both the explosive charge and the ejection charge. Accordingly, a relatively large quantity of explosive had to be built into the projectile, which undesirably restricts the payload.
In order to get by with as small as possible a quantity of explosive and as a result, to be able to provide as large as possible a payload, explosive charges for exploding the projectile casing, or ejection charge for ejecting the payload, were replaced with an opening charge. These charges may be considerably smaller than the explosive charge or ejection charge. In principle, the opening charge is used only for producing lateral openings in the projectile casing along a plurality of casing lines, whereupon the parts of the projectile casing released are removed in a tangential direction relative to the rest of the projectile. The payload which is no longer contained by the outer shell is released as a result. The discharge of the payload happens as follows: before its destruction, the projectile casing exerts a centripetal force on the payload, which as a result of the spin of the projectile, rotates around the longitudinal axis of the projectile. This centripetal force ceases with the destruction of the projectile casing because of the production of the openings in it by the opening charge so that with the action of centrifugal force, the payload leaves its original location and departs in the tangential direction from the projectile or from the rest of the projectile. The tangential component of the payload velocity thus produced is added to the axial component of the payload velocity, which is the same in magnitude and direction as the flight velocity of the projectile. If the payload is divided into coaxial columns, then each column continues to fly at a certain angle of departure relative to the flight path of the projectile, wherein the flight paths of the columns constitute the generatrix of a cone, whose axis is the flight path of the projectile and whose apex is the location of the payload release.
The above described kind of payload release takes place successfully only if the projectile spin is completely transmitted to the columns of the payload before the opening of the projectile casing. Then the payload may be driven in rotation around the longitudinal projectile axis at a resulting tangential velocity component when the columns are released.
At the same time as the rotation around the projectile axis, the payload rotates around itself, i.e., an individual rotation, which may be described as spin. Thus, both before and after release, the payload rotates around its own axis. The advantageous function of this individual rotation or spin is described in more detail below.
So that the spin of the projectile is transmitted to the payload, the above-mentioned tangential component of velocity, which causes the payload to leave the payload chamber, is produced. The payload must be fixed in the payload chamber so that it does not rotate relative to the projectile casing. To that end, U.S. Pat. No. 603,525 discloses that the payload is divided into coaxial columns and that the payload chamber is recessed on the inside so that it has grooves which extend axially. The grooves are approximately the shape of a half-cylinder, whose diameter is the same as that of the columns and in which the columns are disposed.
In order to open the projectile casing as intended in zones along casing lines and in order to keep the quantity of the required explosive as low as possible, known projectiles include a projectile casing that is recessed so that a plurality of intended break zones, running at least approximately axially and evenly distributed over the circumference, open for deploying the columns as a result of the action of the ignited explosive.
As discussed in U.S. Pat. No. 603,525, the intended break zones, although not expressly described as such, are produced by the grooves with the approximately half-cylindrical shape used to tangentially fix the layer of columns resting against the projectile casing, i.e. the outermost layer, relative to the projectile. These grooves extend axially along the inner wall of the sub-projectile chamber and result in the fact that the projectile casing has changing wall thicknesses in the circumferential direction. The intended break zones naturally coincide with the regions of the lowest wall thickness. The intended break zones are more efficient the more abruptly the wall thickness changes.
For the further use of the payload, it is of the utmost significance that the payload not be damaged in the detonation of the opening charge in the explosive chamber. For example, U.S. Pat. No. 603,525 produces a pressure wave in the explosion of the opening charge which naturally acts upon the comparatively weak base plate. Accordingly, it is not certain that detonation of the opening charge is used exclusively for breaking open the projectile casing. Consequently, there is the danger of damaging the payload prior to release.